Cooled lighting apparatus and method

ABSTRACT

An improved apparatus and method for illuminating optical fibers includes a bezel block for positioning the ends of optical fibers near an area of illumination that is isolated from the heat of the source of illumination and that is cooled by air flowing through the block. Heat is transferred from the source of illumination by flowing air which is controlled within an enclosure for maintaining low exhaust temperatures.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of pending application Ser. No. 121,906, filed Nov.17, 1987.

RELATED APPLICATION

The subject matter of this application relates to the subject matterdisclosed in U.S. Patent Application Ser. No. 000,113, now U.S. Pat. No.4,763,984, entitled "Lighting Apparatus and Method" filed on 1/2/87, byGeorge Awai and Michael Ernst.

BACKGROUND OF THE INVENTION

The present invention relates to the apparatus and method forilluminating optical fibers.

Optical fibers are known to the art in several forms. These includedrawn and treated glass and various plastic fibers, any of which mayadditionally be clad or coated. These fibers, typically used in longbundles, transmit light from end to end over substantial distances. Inthe Related Application cited above, the optical fibers additionallyprovide lateral transmission of light which emerges from the sides ofthe fibers to provide illumination along the entire length of the fiber.

Many applications, such as those using multiple fibers in a bundle,require a light source or sources capable of providing light to morethan one end of the fiber bundle. In the Related Application citedabove, illumination is supplied at both ends to provide illumination bymeans of lateral emission of light along the lengths of the fibers, andit has been determined that illuminating both ends of such opticalfibers provides more uniform illumination along the lengths thereof.

Light sources adapted to provide illumination to optical fibers sufferfrom a number of disadvantages. Many sources of illumination becomeoverheated for applications involving plastic fibers, and where thelight source is enclosed within a housing, the housing may becomedangerously hot to the touch. In addition, the heat generated by theenclosed light source may damage various components of the lightingsystem including color filters and the optical fibers themselves.

This danger of overheating has sometimes been overcome by providingforced-air cooling and heat-reflective mirrors. Even with fans, previousdesigns in the prior art restricted the wattage of light bulbs usedwithin the enclosure, typically, to less than 100 watts in order toavoid damaging the optical fibers and associated optical components.This power limitation is considered a serious disadvantage where highlevel illumination is required, such as where lateral transmission oflight from fibers must be visually perceptible against ambient lightlevels.

It is desirable in some applications to provide a light-tight source ofillumination for optical fibers. However, light-tight enclosures oftencontribute to the overheating problem since the enclosure usuallyinterferes with the free flow of cooling air.

Illuminating more than one end of a bundle of optical fibers may beaccomplished with a separate illumination source at each end with theends of the bundled fibers presented to a focused light source. However,where fibers are simply bundled together, it may be difficult to attainregular and easily reproducible results since the bundling may vary fromone installation to the next. Also, it is more difficult to radiate awayaccumulated heat where the fibers are bundled, thus leading to anincreased likelihood of heat-related damage to the fibers.

SUMMARY OF THE INVENTION

In accordance with the present invention, an enclosed source ofillumination for optical fiber cables is provided which eliminatesoverheating problems and which is light tight and which may convenientlyilluminate a plurality of cable ends. In accordance with the presentinvention, a high intensity light source is arranged in housing thatdirects a stream of flowing air around the light source, the fiber endsand the associated components and that then causes the heated air to mixwith ambient temperature air to assure low-temperature operation and alow-temperature exhaust of air from the enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away sectioned view of the light housing forilluminating optical fibers according to the present invention;

FIG. 2 is a plan view of the underside of a chassis constructedaccording to the present invention.

FIG. 3 is a perspective view of the bezel block that houses the ends ofthe optical fibers;

FIG. 4 is a top cut-away sectional view of the block of FIG. 3; and

FIG. 5 is a side sectional view of the block of FIG. 3 showing thecooling passages therethrough.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a cutaway view of the housingaccording to the present invention. A bundle or cable 1 of opticalfibers is positioned within a bezel block 2 consisting of a lower part 3and upper part 5 such that the optical cable 1 has a near end 7 adjacentthe optical window 8 of the bezel block 2 positioned to receive lightfrom light source 9 through the window 8, as illustrated in FIG. 5. Theoptical cable 1 may consist of one or many fibers which, as detailedbelow, may be separated into bunches or bundles. Light from the lightsource 9 enters the optical cable 1 at the near end 7 and is transmittedalong the length of the optical cable 1 for external illuminationapplications.

The light source 9 may be a quartz-halogen bulb which may be energizedin conventional manner using a line-voltage stepdown transformer 13. Thelight source 9 includes an ellipsoidal reflector 15 which focuses thelight on the near end 7 of the optical cable 1. The reflector 15 isformed of a dichroic material which will reflect the desired visiblelight toward the cable 1 but which will transmit the undesired infraredso as to avoid heat buildup near the end of the optical cable 1 whichmay be damaged by excessive heat. A window 29 of dichroic material whichtransmits visible light but reflects heat may be introduced into thelight beam between light source 9 and bezel block 2 to Prevent heatbuild up near the end of the optical cable 1.

The reflector 15 is provided with a mounting flange 23 and brace 25 inorder to maintain the light source 9 in position relative to the bezelblock 2.

A rotatable color wheel 17 may optionally be introduced into the lightpath between source 9 and bezel block 2 to effect a pleasing variationin the color of light transmitted to the optical cable 1. The wheel 17may be rotated by means of a motor 19 and is preferably composed of adichroic material which will transmit the desired colors and reflect theremaining colors including infrared. Such dichroic materials are foundto be more effective in Preventing the heat buildup near the cable endsthan filters consisting of colored glass or gel. The light source 9 andreflector 15 are mounted within an enclosure 27 having a heat-reflectivewindow 29 to permit the illumination of the optical cable 1. Theenclosure may be mounted on a standoff 31 which is fastened to thechassis 33.

A fan 35 is positioned downstream of the light source 9 within thehousing 4 to promote air circulation by creating an air stream throughthe housing 4. The housing includes an upper case 37 and a lower case 39and includes primary entrance holes 41 and primary chassis holes 45located upstream of the light source 9 to permit the flow of air throughthe housing. Additionally, case exhaust holes 49 and chassis exhaustholes 53 provide exit passages for heated air from the interior of thehousing. As discussed below, the holes through the housing 4 should belarge relative to the holes through the chassis 33 so that the directionand speed of the airflow may be determined by the size and placement ofthe chassis holes.

In operation, the fan 35 creates a pressure differential for moving airthrough the housing 4. The fan 35 and the bracket 55 upon which it ismounted will preferably closely fit the interior dimensions of thehousing to promote flow of air within the housing entirely through thefan 35.

Air at ambient temperature is drawn through the primary entrance holes41 and through the smaller chassis holes 45 which are oriented in closeproximity to the hot light source 9. The use of small holes relative tothe airflow generated by the fan 35 causes a relatively high-sPeedstream of air at ambient temperature to enter the interior of thehousing. By suitably positioning the chassis holes 45 the stream of airat ambient temperature air may be directed toward the components such asthe bezel block 2 and the light source 9 and reflector 15 within theenclosure 27 for which cooling is most crucial. The enclosure 27includes vents 61 to direct the passage of cooling air therethrough andaround the light source 9.

It has been found that air flowing at high speed across the hot lightsource 9 is preferred over passing large volumes of air at low speedover the light source 9 for removing heat from the source. Thus, thevarious holes described herein are sized to develop high-speed airstreams.

At least one hole 45 in the chassis 33 is Positioned to direct a flow ofair across and through the bezel block 2 as discussed more fully below.

It has been found that the passage of air across the hottest elements(i.e. the light source 9, reflector 15, and bezel block 2) causesflowing air to undergo a large rise in temperature, on the order of 60degrees Fahrenheit for a bulb of approximately 100 to 150 watts rating.Where the ambient temperature of air exceeds 70 degrees Fahrenheit, thisheating of the air circulating within housing 4 may contribute tofailure of such components as the fan 35, the color wheel motor 19 andthe stepdown transformer 13 due to overheating. Additionally, thehousing 4 may become uncomfortably or dangerously hot to the touch. Ifthe fan 35 generates a circular airflow against the top, back, andbottom of the interior of the housing, there may be relatively littleairflow that is within the central region of the housing while much heatis transferred to the exterior of the housing.

Referring additionally now to FIG. 2, the chassis 33 is provided withauxiliary holes 63 located upstream of the fan 35. These holes 63 assistin the general cooling of the structure according to this invention byadmitting air at ambient temperature which mixes with the heated airthat has already passed over and through the light source 9, bezel block2 and reflector 15. This mixing of high-speed heated air with air atambient temperature results in larger volume of exhaust air at lowertemperature. This lower-temperature air is less likely to causeoverheating failures of the fan 35 and other components. Additionally,lower temperature air is less likely to transfer heat to the exteriorcase 37, 39 so as to cause the exterior surfaces to become hot.

It has been found that a fan 35 with an air-flow rating of 90 cubic feetper minute adequately cools the housing 4 and components that areconstructed and arranged therein according to the present inventionusing a light source 9 comprising an incandescent bulb rated at 200watts and having three three-quarter inch diameter primary holes 45 andfour three-quarter inch diameter auxiliary holes 63, the externaltemperature of an apparatus thus constructed and arranged has been foundto operate at approximately 100 degrees Fahrenheit with air at anambient temPerature of 70 degrees Fahrenheit.

In FIG. 3, there is shown a perspective view of a bezel block 2constructed according to the present invention including a lower block 3and an upper block 5. The color wheel 17 with the associated motor 19and bracket 21 are illustrated as mounted on the upper block 5. Fourports 71, 72, 73, 74 are provided to accept bundles of optical fibers(not illustrated) for positioning within the interior of the bezelblock, as later described herein.

Referring now to FIG. 4, there is shown a cut-away top view of thebottom block 3. The top block 5 may typically be formed substantially inmirror image of the bottom block 3. The outer ports 71, 74 couple to theouter ducts or channels 75, 78, and the inner ports 72, 73 couple to theinner ducts or channels 76, 77 at the central chamber 79 which may bedivided by a barrier 81. Thus, a bundle of one or more optical fibers(not pictured) may be inserted through a port 71. Because such bundle(not pictured) is relatively laterally flexible, it may be guided by thesides of duct 75 toward the barrier 81 where the optical fibers of acable may join with the fibers of another cable that is similarly guidedto the central chamber 79 along duct 76.

Generally, the highest degree of light transmission in optical fibersoccurs where the light travels in a path substantially parallel to theaxis of the optical fiber. As the angle of the light within the opticalfiber approaches a critical angle relative to the axis of the fiber, thelight exits through the surface of the fiber. Because the barrier 81 isdisposed along an axis parallel to a desired direction of illumination,the positioning of the optical fibers in the cables against the barrier81 causes the fibers to be generally aligned in the direction ideallysuited for efficient end illumination.

The bezel block 2 may be made of suitable material, such as aluminum orwhite (or light-colored) Plastic having good spectral reflectiveproperties. These reflective materials provides an advantage inilluminating optical fiber bundles in that light which escapes laterallyfrom the bundles may be re-reflected by the light-colored and reflectiveinterior walls of the ducts 75, 76, 77, 78 back into a fiber forefficient illumination of the fibers by the light source 9.

The bezel block 2 provides standardization of positioning of the ends ofoptical fibers for maximally efficient illumination. Thus, even where itis necessary to exchange or replace a cable of optical fibers the fibersmay be inserted via ports 71-74 and ducts 75-78 into proper position foruniform illumination characteristics from one installation to the next.Similarly, for devices mass produced according to the present invention,the bezel block 2 serves as an assembly guide leading to more rapidmanufacture, and greater consistency in results and greater ease inidentifying faulty components. The ducts 75-78 are contoured to avoidbending a fiber at an angle acute enough to cause light to exit throughthe surface of the fiber.

Additionally, a bezel block 2 formed of plastic material provides heatinsulation for the protection of the relatively heat-intolerant plasticoptical fibers from heat damage. Alternatively, a material such asaluminum may be used where ample cooling of the block is provided orwhere less heat-sensitive glass fibers are used. To further aid inmaintaining the bezel block and the optical fibers housed therein at lowoperating temperatures, ventilation of the block is provided by means ofthrough-holes 85 and 87 and 89. The ends of the optical fibers areilluminated in the vicinity of the illumination window 8 which the ends7 of the optical fibers are positioned. The ends are thereforepositioned substantially in the place of maximally-focused light fromsource 9. As an unwanted consequence of focusing visible light at thislocation, infrared radiation may also be concentrated at such location.Accordingly, ventilating holes 87, 89 are disposed in close associationwith the ends 7 of the optical fibers to promote cooling by convectionvia air flowing through the housing and bezel block 2.

FIG. 5 is a simplified cross-sectional view of the bezel block 2 whichillustrates pictorially the orientation of optical fiber within a ductto the illumination location. The block 2 includes an upper part 5 and alower part 3 and includes a forward vent hole 87 into chamber 96 andanother vent hole 89, through the forward position of a duct 75 near thelocation at which the ends 7 of the optical fibers are illuminated. Theends of the optical fibers to be illuminated are positioned near, butpreferably not in contact with, a first window 92 of dichroic materialwhich is spaced from a second window 95 of dichroic material or plainglass to form the chamber 96 between them.

Cooling is enhanced by passing air through the chamber 96 and throughthe forward end of the duct 75. This air flows through a notch 97disposed beneath the motor 19 which is thereby cooled by the flow ofair. The vent hole 87 passes air through the chamber 96 formed betweenthe windows 92, 95 to assure that the first window 92 is maintained cooland to reduce the possibility of heat buildup and transfer to the ends 7of the optical fibers 1 by convection or conduction. Preferably, thewindows 92, 95 are formed of materials which reflect infrared radiationbut transmit visible light. The Spring 93 may be a generallyrectangular, U-shaped spring that is situated within the chamber 96 atthe extreme edges of the windows 92, 95 to permit light to pass throughthem without interference. Any means of urging the two windows apartwhich does not interfere with the passage of light may also be used.Preferably, the upper block 5 and lower block 3 are constructed with arestraining edge about the illumination port 8 to facilitate theplacement and easy slide removal of the windows for cleaning orreplacement.

In accordance with one embodiment, the light source 9 is an incandescentbulb having a filament 101 that is positioned substantially within thecircle described by the foci of the ellipsoidal reflector 15 and that isoriented perpendicular to the direction of illumination. It has beenfound that such orientation and positioning of the filament 101increases the efficiency of illumination of optical fibers because thereflected light describes a generally smaller steradian angle than isfound with the filament 101 is oriented parallel to the direction ofilumination in a similarly dimensioned reflector.

What is claimed is:
 1. A lighting apparatus for optical fiberscomprising:a case having an aperture for admitting optical fibers and ameans for positioning optical fibers; an airflow means for inducing aflow of air through and within said case; a light source disposed tosupply light to an end of an optical fiber; exhaust holes communicatingthe interior with the exterior of said case whereby the flow of airinduced by said airflow means may be exhausted from the interior of saidcase; a first air intake means adapted to admit a stream of ambient airfrom the exterior of said case to the interior of said case andadditionally to direct said stream of air across said light source; anda second air intake means adapted to admit ambient air into the interiorof said case there to mix with said stream of air which has beendirected across said light source.
 2. A lighting apparatus as in claim 1wherein said airflow inducing means is an electric fan.
 3. A lightingapparatus as in claim 1 wherein said light source comprises anincandescent bulb and a reflector.
 4. A lighting apparatus as in claim 3wherein said reflector comprises a dichroic material formed into anellipsoidal reflector and where the filament of said incandescent bulbis disposed substantially perpendicular to the direction of illuminationand is disposed within a circle described by the foci of the ellipsoidalreflector.
 5. A lighting apparatus as in claim 1 wherein said first airintake means comprises a plurality of holes and wherein second airintake means comprises a plurality of holes.
 6. A lighting apparatus asin claim 5 wherein said light source is disposed substantially betweenthe holes comprising said first air intake means and said airflow meanswhereby the flow of air induced through said first air intake means willbe directed across said light source.
 7. A lighting apparatus as inclaim 6 wherein the holes comprising said second air intake means arelocated substantially remote from the holes comprising said first airintake means, said second air intake means having a larger total areathan said first air intake means.
 8. A lighting apparatus as in claim 7wherein the holes comprising said second air intake means describe anarea approximately one-third greater than the area described by theholes comprising said first air intake means.
 9. A lighting apparatus asin claim 1 comprising at least one optical filter means disposedintermediate the light source and said end of said optical fiber whereinsaid optical filter means is adapted to transmit desired lightwavelengths and reflect undesired wavelengths.
 10. A lighting apparatusas in claim 1 wherein said means for positioning optical fiberscomprises a plurality of passages therethrough adapted to permit thepassage of cooling air therethrough.
 11. A lighting apparatus as inclaim 10 comprising a pair of spaced, substantially transparent windowslocated adjacent said end of said optical fiber and through which saidlight source may illuminate said end, said windows further adapted andlocated to permit a flow of cooling air therebetween.
 12. A lightingapparatus as in claim 11 wherein said windows are located within saidmeans for positioning optical fibers and wherein openings through saidmeans for positioning optical fibers are provided to permit the flow ofair between said windows.
 13. The method of illuminating a plurality ofoptical fibers from a light source comprising the steps of:bundling theoptical fibers to substantially align the fibers near a common endthereof; focusing the light source within an area approximately thesectional area of the bundled end of the optical fibers; positioning thebundled end of optical fibers near the focused area of light; generatinga flow of air past said light source so as to provide cooling; providinga second flow of air to mix with said first flow of said, said secondflow of air not being substantially directed past said light source; andilluminating the light source.
 14. The method of claim 13 comprising thesteps of:interposing a stream of moving air between the light source andthe bundled end of the optical fiber.
 15. The method of claim 14comprising the step of providing transparent barriers axially spacedbetween the bundled end of optical fibers and the light source along theaxis of transmitted light wherein a stream air is passed between saidtransparent barriers.
 16. The method of claim 13 wherein the step ofgenerating a flow of air is accomplished by providing a fan having an upstream side and down stream side and placing said fan within a housingwhich also encloses said light source and said bundled end of opticalfibers whereby an upstream area and a downstream area are defined withinsaid housing whereby air will tend to move from said upstream area tosaid downstream area;said step of providing a first stream of airfurther characterized by placing an aperture in said housing in closeassociation with said light source whereby air drawn in through saidaperture from the exterior of said housing will be directed toward saidlight source; and said step of providing a second air source furthercharacterized in locating apertures capable of admitting exterior airremote from said first apertures such that the stream of air enteringtherethrough will not be substantially directed against said lightsource; and mixing said first stream and second stream of air.